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-<refentry id="func-open">
- <refmeta>
- <refentrytitle>V4L2 open()</refentrytitle>
- &manvol;
- </refmeta>
-
- <refnamediv>
- <refname>v4l2-open</refname>
- <refpurpose>Open a V4L2 device</refpurpose>
- </refnamediv>
-
- <refsynopsisdiv>
- <funcsynopsis>
- <funcsynopsisinfo>#include &lt;fcntl.h&gt;</funcsynopsisinfo>
- <funcprototype>
- <funcdef>int <function>open</function></funcdef>
- <paramdef>const char *<parameter>device_name</parameter></paramdef>
- <paramdef>int <parameter>flags</parameter></paramdef>
- </funcprototype>
- </funcsynopsis>
- </refsynopsisdiv>
-
- <refsect1>
- <title>Arguments</title>
-
- <variablelist>
- <varlistentry>
- <term><parameter>device_name</parameter></term>
- <listitem>
- <para>Device to be opened.</para>
- </listitem>
- </varlistentry>
- <varlistentry>
- <term><parameter>flags</parameter></term>
- <listitem>
- <para>Open flags. Access mode must be
-<constant>O_RDWR</constant>. This is just a technicality, input devices
-still support only reading and output devices only writing.</para>
- <para>When the <constant>O_NONBLOCK</constant> flag is
-given, the read() function and the &VIDIOC-DQBUF; ioctl will return
-the &EAGAIN; when no data is available or no buffer is in the driver
-outgoing queue, otherwise these functions block until data becomes
-available. All V4L2 drivers exchanging data with applications must
-support the <constant>O_NONBLOCK</constant> flag.</para>
- <para>Other flags have no effect.</para>
- </listitem>
- </varlistentry>
- </variablelist>
- </refsect1>
- <refsect1>
- <title>Description</title>
-
- <para>To open a V4L2 device applications call
-<function>open()</function> with the desired device name. This
-function has no side effects; all data format parameters, current
-input or output, control values or other properties remain unchanged.
-At the first <function>open()</function> call after loading the driver
-they will be reset to default values, drivers are never in an
-undefined state.</para>
- </refsect1>
- <refsect1>
- <title>Return Value</title>
-
- <para>On success <function>open</function> returns the new file
-descriptor. On error -1 is returned, and the <varname>errno</varname>
-variable is set appropriately. Possible error codes are:</para>
-
- <variablelist>
- <varlistentry>
- <term><errorcode>EACCES</errorcode></term>
- <listitem>
- <para>The caller has no permission to access the
-device.</para>
- </listitem>
- </varlistentry>
- <varlistentry>
- <term><errorcode>EBUSY</errorcode></term>
- <listitem>
- <para>The driver does not support multiple opens and the
-device is already in use.</para>
- </listitem>
- </varlistentry>
- <varlistentry>
- <term><errorcode>ENXIO</errorcode></term>
- <listitem>
- <para>No device corresponding to this device special file
-exists.</para>
- </listitem>
- </varlistentry>
- <varlistentry>
- <term><errorcode>ENOMEM</errorcode></term>
- <listitem>
- <para>Not enough kernel memory was available to complete the
-request.</para>
- </listitem>
- </varlistentry>
- <varlistentry>
- <term><errorcode>EMFILE</errorcode></term>
- <listitem>
- <para>The process already has the maximum number of
-files open.</para>
- </listitem>
- </varlistentry>
- <varlistentry>
- <term><errorcode>ENFILE</errorcode></term>
- <listitem>
- <para>The limit on the total number of files open on the
-system has been reached.</para>
- </listitem>
- </varlistentry>
- </variablelist>
- </refsect1>
-</refentry>